1. Technical Field
The present invention relates to an acceleration sensor, particularly to a vibration acceleration sensor, which detects a magnitude of acceleration by utilizing the change of frequencies caused by acceleration.
2. Related Art
Some acceleration sensors utilize the resonance phenomenon of vibrating body. These vibration acceleration sensors detect resonant frequency of the vibrating body, so as to perceive the magnitude of acceleration. Thus, it is easy to digitalize a detector circuit as well as to make the circuit smaller. In JP-A-9-257830, a vibration acceleration sensor is suggested, in which a vibrating body is arranged having a thin contact unit between a support and a mass. The acceleration sensor recited in JP-A-9-257830 can be manufactured with a silicon substrate, utilizing micromachining techniques.
However, since the above-described acceleration sensor contains semiconductors, a special external force is required in order to excite the vibrating body, and the frequency-temperature characteristic of the sensor is poor, requiring a separate units such as a circuit that compensate temperatures. Moreover, such acceleration sensor does not detect acceleration unless a stress based on a certain degree of acceleration is imposed on the sensor, making it difficult for the sensor to have high sensitivity.